A rotor of an air turbine for dental drills comprises a shaft mounted in ball bearings or in one or more air bearings. The shaft is provided with a chamber accommodating a mechanism for fixing the burr. The nose of the turbine, of course, is bored to receive a shaft passing therethrough.
In the head of the turbine, the rotor is suspended from rings of soft material or O-rings which thus support the turbine, particularly laterally. This means that the rotor may be displaced laterally upon a pressure exerted on the turbine head. In consequence, the diameter of the bore provided in the turbine nose must be much larger than that of the shaft, in order to prevent the rotating shaft from butting against and produce friction at the bore wall. A gap is therefore left between the shaft and the bore in the turbine nose through which dentine, powdered enamel, blood, filling residues, and other waste might infiltrate during the operation of the turbine. Such waste is projected up to the inside ball bearing, or the air bearing and the air inlets which thus become fouled and clogged. This strongly affects the reliability of dental turbines. Their ball bearings or air bearings and air inlets must periodically be cleaned or even replaced. Further, waste of any kind accumulating in the interior of the turbines may become a non-negligible source of infection.